Predicting the Distribution of Naturally Occurring Phosphatic Soils across a Countywide Landscape, Florida, USA

Abstract

We used a GIS approach to test a conceptual soil-landscape model which integrates topographic, geologic and soil information for predicting the distribution of phosphatic soils. The hypothesis was that phosphatic soils occur on erosional landscapes where phosphatic geologic materials are exposed at or near land surface. Areas of high (scarp), medium (plain), and low (plateau) likelihood of such exposure were delineated based on topographic and geologic information. An initial predictive phosphatic soils map was created and validated by field sampling. Samples were taken at two depths: upper (0–25 cm) and lower (100–125 cm); and the total phosphorus (TP) was determined. Mean TP concentration for the lower depth was 6195 mg kg−1 for the scarp, 2485 mg kg−1 for the plain, and 193 mg kg−1 for the plateau. The initial map was revised to show that the probability of finding a phosphatic soil was highest for the scarp region (73%), medium for the plain region (33%), and lowest for the plateau region (7%).